This invention relates generally to straps for wrist instruments, especially wristwatches and relates to improved clasps for attaching the strap ends around the wrist of the wearer. More particularly, the invention relates to an improved wristwatch flexible strap and clasp attachment.
Conventional wristwatches are held on the wrist by leather, metal or plastic straps, bands or bracelets, which may be expanded to go over the wrist or attached around the wrist by attaching strap ends with buckle, clasp or other type of detachable fasteners. This invention relates to wristwatch attachments employing a flexible strap with a pair of strap ends. Typically, the strap ends are connected with a buckle which provides for adjustment of the strap length. The buckle adds to the thickness of the strap, requires a "keeper" to keep the tongue of the strap in place, and sometimes is unsightly or has corners which catch upon sleeves or clothing.
Other types of clasps have been suggested for jewelry, wrist instruments and wristwatches for straps with overlapping strap ends. One design has opposing members coated with fibrous material on one strap end and a layer of material having resilient hook-like members on the other strap end (sold under the registered trademark Velcro .RTM.), such a construction being shown in Montague U.S. Pat. No. 3,747,171, issued July 24, 1973. Another type of bracelet clasp suitable for a strap of flexible thermoplastic material such as polyurethane comprises a sleeve on one strap end with transverse internal teeth and a tongue on the other strap end with complementary nesting teeth, such a construction being shown in Bollinger U.S. Pat. No. 4,615,185, issued Oct. 7, 1986. Such construction requires a sleeve to provide a transverse holding force to maintain the complementary teeth engaged.
Permanent magnets have been suggested in the past for providing a separable clasp for jewelry, animals' collars or the like. For example, Loofboro U.S. Pat. No. 2,648,884, issued Aug. 18, 1953 describes a magnetic clasp of two rigid, two-pole, permanent magnets with an interlocking tongue and groove connection to mechanically lock the sections against relative sliding movement tending to separate the clasp. Another magnetic clasp which is intended to disengage without catching is provided for animal collars as shown in Krebs U.S. Pat. No. 3,589,341, issued June 29, 1971. Still another magnetic clasp for jewelry having two rigid co-acting magnets encased in plastic sheaths discloses a variety of mechanical interlocking protuberances and indentations to prevent sliding separation of the magnetically attracted members.
Holtz U.S. Pat. No. 4,255,837 issued Mar. 17, 1981 and Maehaski U.S. Pat. No. 4,620,725 issued Nov. 4, 1986 each show a pair of sheets of flexible synthetic resin having magnetizable powder therein, permanently magnetized into rows of alternating magnetic polarity providing a holding force between sheets. However, there are no provisions for ridges, protuberances or teeth preventing sliding movement between the magnetically attracted surfaces.
Accordingly, one object of the present invention is to provide an improved flexible strap and clasp attachment for a wristwatch.
Another object of the invention is to provide an improved clasp for a flexible strap which eliminates buckles or other types of protruding members thereby permitting a thinner, more comfortable flexible strap attachment.
Another object is to provide an improved clasp for a wristwatch which is secured, yet easy to engage when desired.